Brake drum truing method and apparatus

ABSTRACT

Apparatus and method for redefining the central opening through a brake drum so that the central opening is concentric with respect to the lug hole arrangement in the brake drum wherein the apparatus includes a support means carrying a plurality of support pins which engage and support the brake drum through its lug holes, a tool for selected engagement with the brake drum about its central opening and positioning means for locating the tool along the effective rotational axis of the brake drum when carried by the support means so that the tool can engage the drum and redefine the central opening concentric about the rotational axis and within the lug hole arrangement. The support pins may be mounted in an adapter so as to provide for different lug hole arrangements. The method includes supporting a brake drum to have its central opening redefined; positioning a tool concentrically within the lug hole arrangement; and engaging the brake drum about its central opening with the tool while maintaining its concentricity with respect to the lug hole arrangement to redefine the central opening.

United States Patent Ratteree et al.

[ BRAKE DRUM TRUING METHOD AND APPARATUS [72] Inventors: James Ratteree,4126 Flat Ridge Drive, Stone Mountain, Ga. 30083; James A. Seaman, 4900Northside Drive, N.W., Atlanta, Ga. 30309 [22] Filed: Nov. 5, 1970 [21]Appl.No.: 87,146

Related US. Application Data [63] Continuation-impart of Ser. No.40,120, May 25,

[451 July 18, 1972 757,950 4/1904 McElwain et al ..408/84 PrimaryExaminer-Leonidas Vlachos Attorney-B. J. Powell 57] ABSTRACT Apparatusand method for redefining the central opening through a brake drum sothat the central opening is concentric with respect to the lug holearrangement in the brake drum wherein the apparatus includes a supportmeans carrying a plurality of support pins which engage and support thebrake drum through its lug holes, a tool for selected engagement withthe brake drum about its central opening and positioning means forlocating the tool along the effective rotational axis of the brake drumwhen carried by the support means so that the tool can engage the drumand redefine the central opening concentric about the rotational axisand within the lug hole arrangement. The support pins may be mounted inan adapter so as to provide for different lug hole arrangements.

The method includes supporting a brake drum to have its central openingredefined; positioning a tool concentrically within the lug holearrangement; and engaging the brake drum about its central opening withthe tool while maintaining its concentricity with respect to the lughole arrangement to redefine the central opening.

10 Claims, 7 Drawing Figures Patented July 18, 1972 3,677,655

3 Sheets-Sheet 1 fig... Z2 6 42 75 2c Patented July 18, 1972 3,677,655

3 Sheets -Sheet 3 Patented July 18, 1972 3 Sheets-Sheet 5 1 BRAKE DRUMTRUING METHOD AND APPARATUS CROSS-REFERENCE TO APPLICATIONS BACKGROUNDOF THE INVENTION On vehicles equipped with drum type brakes, the brakingsurfaces inside the brake drums frequently lose their concentricity withrespect to the efiective rotational axis of the drum therebynecessitating returning of the drums to re-establish the concentricity.This loss of concentricity is due primarily to the fact that the brakeshoes do not expand in such a manner as to maintain equal contact alongall portions of the shoes and results in loss of braking efficiency.

Most brake drum lathes which are used to re-turn the braking surfaces ofthese drums support the drums by the central opening definedtherethrough while turning same. This arrangement has provensatisfactory for supporting those brake drums which are also supportedon the vehicle by this central opening. Certain brake drums are not,however, supported through this central opening but rather through thelug holes by the lug bolts on a spider carried by the wheel assembly.This is generally the case with most rear wheel assemblies. Because thebrake drum is not supported by this central opening, the dimensional andlocation tolerances are not sufficient to insure concentricity of thisopening and the braking surface, resulting many times in the brakingsurface, when returned, to still be out of concentricity with theeffective rotational axis of the brake drum.

SUMIVIARY OF THE INVENTION These and other problems and disadvantagesassociated with prior art techniques for refinishing or returningbraking surfaces of brake drums supported on the vehicle through the lugholes rather than the central opening are overcome by the inventiondisclosed herein by re-locating the central opening concentrically withrespect to the effective rotational axis of the brake drum while it ison the vehicle. This is accomplished using the lug hole circle to locatethe opening under a cutting tool since the lug hole circle is alwaysconcentric about the effective rotational axis of this type of brakedrum. An adapter is provided which includes a plurality of locating pinswhich fit in the lug holes of the drum and locate the cutting toolconcentrically within the lug hole circle to insure that the centralopening through the drum will be trued.

The method of the invention includes the steps of locating a cuttingtool concentrically with respect to the lug hole circle in the drum andengaging the drum about its central opening with the too] whilemaintaining the concentricity to cause the tool to relocate the openingconcentrically with respect to the lug holes.

The apparatus of the invention includes a portable version and astationary version. The portable version includes a support member whichcarries a plurality of pins corresponding in location and number to thatof the lug holes in the brake drum. A cutting tool is rotatably mountedin the support member concentrically with respect to the pin arrangementand is spring urged away from the plane of the drum when positioned onthe drum but can be selectively moved into engagement with the drumabout the central opening to redefine the central opening concentricwith the lug hole circle.

The stationary or table version includes a base member which defines apositioning recess therein with an adapter releasable carried by therecess. The adapter has a first set of pins on one side thereof whichcorrespond in location and number with the lug holes in a first sizebrake drum. The adapter also has a second set of pins which correspondin location and number to another set of lug holes in a difi'erent sizedrum. Both sets of pins are arranged so as to position the brake drumabout a common centerline on the base member about which the lug holecircle of the drum is concentric. The

base member also rotatably mounts a cutting tool along the commoncenterline above the adapter. The tool is spring urged away from theadapter to facilitate the placement of the drum on the adapter, but canbe moved into engagement with the drum to redefine the central openingconcentric with the lug hole circle. The pins in the adapter may bespring loaded to facilitate the seating of the drum on the adapter.

These and other features and advantages of the invention will becomemore fully understood upon consideration of the following specificationand accompanying drawings in which like characters of referencedesignate corresponding pans throughout the several views and wherein.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showingthe portable embodiment of the invention ready for use;

FIG. 2 is a front elevational view of that embodiment of the inventionshown in FIG. 1;

FIG. 3 is a cross-sectional view taken substantially along line 3-3 inFIG. 2;

FIG. 4 is a side elevational view showing that embodiment of theinvention of FIG. 1 in use;

FIG. 5 is a cross-sectional view of the adapter of the second embodimentof the invention;

FIG. 6 is a perspective view of the second embodiment of the invention;and,

FIG. 7 is an elevational view of the second embodiment of the inventionshown partly in cross-section with the inventionin use.

These figures and the following detailed description disclose specificembodiments of the invention, however, it is to be understood that theinventive concept is not limited thereto since it may be embodied inother forms.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS Referring specificallyto FIGS. 1-4, it will be seen that the first embodiment of the inventionor portable device 10 in cludes a housing 11 carrying a plurality ofsupport pin assemblies 12 and a cutter assembly 14.

The housing 11 is generally disk shaped and defines an axially extendingbore 15 along the centerline CL thereof as best seen in FIG. 3. Theworking face 16 of housing '11 defines a counterbore 18 thereinconcentrically about the end of bore 15 which receives the cutting tooltherein as will be explained later. The bore 15 receives a bushing 19therein which rotatably supports the cutter assembly '14 as describedbelow.

The housing 11 also defines a plurality of pin receiving passages 20therethrough which are parallel to the bore 15 and equally spaced fromeach other along'a circle C (see FIG. 2) concentric with bore 15. Thecircle C corresponds in diameter to the lug hole circle of a specificsize brake drum D as seen in FIGS. 1 and 4 and the passages 20correspond in number to the lug holes H through the drum D to be usedwith the device 10.

The pin assemblies 12 are positioned in the passages 20 and project outfrom the working face 16 of housing 11. Each pin assembly 12 includes abushing 21 with an annular flange 22 at one end thereof which fits in acomplementary recess 24 about that end of passage 20 opening ontoworking face 16. A support pin 25 having an enlarged head portion 26 anda reduced diameter shank portion 28 is provided for each assembly 12 asseen in FIG. 3. The reduced diameter portion 28 is just sufficient to bereceived in the passage 29 through bushing 21 thus leaving the headportion 26 exposed over the working surface 16 of housing 11. The headportion 26 of each support pin 25 is tapered at the extending endthereof as indicated at 30 to facilitate the insertion of the pins 25 inthe lug holes H as best seen in FIG. 4.

To retain each pin assembly 12 in place, the extending end of each shankportion 28 is tapped and a retaining ring 31 is attached to each of theassemblies 12 through fasteners 32 engaging the tapped ends of shankportions 28. This clamps the housing 11 between the ring 31 and theflange 22 of bushing 21 to hold the assemblies 12 in place. Since thepin assemblies 12 are concentrically located about the centerline CL ofthe portable device 10, the centerline CL will lie along the effectiverotational axis of a brake drum D supported on a vehicle (not shown)through its lug holes H when the tapered ends 30 of the pins 25 arepositioned in the lug holes of the drum as seen in FIG. 4.

The cutter assembly 14 is carried in bore 15 as best seen in FIG. 3 andincludes a spindle 40 which is rotatably positioned in bushing 19carried in bore 15. That end of spindle 40 extending into counterbore 18is threaded to receive a nut 41 thereon (see FIG. 2) to position acutting tool 42 on the lower end of spindle 40. The spindle 40 isprovided with a shoulder 44 which prevents the tool 42 from striking theend of counterbore 18 as the spindle 40 is moved upwardly as seen inFIG. 3.

A collar 45 is positioned on the spindle 40 above the housing 11 byscrew 46 and maintains a spring 48 around spindle 40. The spring 48extends between the collar 45 and top of housing 11 to constantly urgethe spindle 40 so as to retract the tool 42 within the counterbore 18. Ahandle 49 is mounted at the upper end of spindle 40 for selectivelyrotating the spindle and cutting tool 42 and for causing the tool to beextended from counterbore 18 and engage the brake drum D about itscentral opening as seen in FIG. 4 when the handle 49 is depressed.

In operation, it will be seen that the device 10 is used by placing thetapered ends 30 of pins 25 in the lug holes H of the drum D as seen inFIG. 4. While the device 10 is shown on the inside of the drum in FIG.4, it is to be understood that the device 10 could just as easily beused from the other side of the drum D. When the pins 25 are in the lugholes H, this lines up the centerline CL of the device 10 with theefifective rota tional axis of the drum while it is mounted on thevehicle. Since the cutting tool 42 is always maintained concentric aboutthe centerline CL, it can be moved into engagement with the drum aboutthe central opening 0 to redefine the opening 0 so that it is concentricwith respect to the effective rotational axis of the drum and the lughole circle C. This allows the drum D to then be mounted on aconventional brake drum lathe (not shown) and the braking surface BSre-turned so that it is concentric with the efiective rotational axis ofthe drum.

Referring now to FIGS. -7, the device 100 is a stationary version of theinvention. The device 100 includes a base member 101 adapted to sit on atable and defining a bore 102 therethrough with a counterbore 104 at theupper end thereof which opens onto the upper working surface 105 of thebase member 101. The juncture of the bore 102 and counterbore 104provides a shoulder 106 as will be explained below. Both bore 102 andcounterbore 104 are concentric about common centerline CL.

The base member 101 also defines a passage 108 therethrough which isdisplaced laterally from the bore 102 and which has its axis parallel tothe centerline CL. The base member is split at passage 108 and providedwith a fastener 109 therethrough to reduce the diameter of passage 108and clamp an upstanding standard 110 therein as seen in FIGS. 6 and 7.It will be seen that standard 1 extends above the base member 101parallel to the centerline CL of bore 102 and counterbore 104.

A positioning arm 111 is carried by the standard 110. The arm 11 1defines a passage 112 through one end thereof which is slidablyreceivable around the standard 110 to position the arm 111 parallel tothe working surface 105 of base member 101. The arm 1 1 l is split atthe passage 1 12 and provided with fastener 114 to selectively clamp thearm 111 at any position vertically along standard 110. The standard 110and passages 108 and 112 have a square cross-section so as to maintainthe rotational position of the arm 111 fixed with respect to standard110 as the arm is selectively moved along the standard 1 10.

The extending end of arm 111 defines a passage 115 therethrough whichhas its axis aligned with the centerline CL of bore 102 and counterbore104. A journal bearing 116 is provided in passage 115 which mounts thecutter assembly 120.

The cutter assembly 120, like the cutter assembly 12, in-

I cludes a spindle 121 which is rotatably and slidably received throughjournal bearing 116. The spindle 121 is adapted to receive a cuttingtool 122 on its lower end extending below arm 111 and held thereon by anut 124. A collar 125 is positioned on spindle 121 by screw 126 andmaintains a spring 128 around spindle 121 between collar 125 and the topof arm 1 1 1. The spring 128 is effective to constantly urge spindle 121upwardly so as to draw tool 122 away from base member 101 yet will allowthe spindle 121 to be forced downward toward the base member 101.

The upper end of the spindle 121 may be provided with a handle formanually rotating the spindle and tool 122 as with the device 10,however, a motor 129 is shown with its drive shaft 130 attached to theupper end of spindle 121. The motor 129 is carried by spindle 121 and ismovable therewith. A guide 131 is carried by arm 111 and extends upbeside motor 129 to be engaged by a tongue 132 on motor 129 forpreventing rotation of motor 129 when it is rotating spindle 121. Ahandle 134 is also provided on motor 129 for forcing the motor andspindle 121 as well as tool 122 downwardly toward base member 101.

An adapter as seen in FIGS. 5 and 7 is provided for holding the brakedrum D in the proper position for the tool 122 to redefine the centralopening 0 in the drum so that it is concentric with the effectiverotational axis of the drum. The adapter 140 includes a disk shapedbacking plate 141 having a diameter just sufficient to be received inthe counterbore 104 and rest on shoulder 106 as best seen in FIG. 7.

Referring back to FIG. 5, the plate 141 defines a central opening 142therethrough which is larger in diameter than the opening 0 through drumD. The opening 142 is concentric about the centerline XL of adapter 140.When adapter 140 is placed in counterbore 104, the centerline XLcoincides with centerline CL of the counterbore 104. The plate 141defines a first set of recesses 144 therein which open onto one workingface 145 of plate 141. These recesses 144 are circumferentially spacedalong a circle having a diameter corresponding to that of the lug holecircle in one standard brake drum. The recesses 144 also correspond inspacing and number to the lug holes in the brake drum. The plate 141also defines a second set of recesses 146 which open onto the oppositeworking face 148 of plate 141. The recesses 146 are arranged similarlyto recesses 144 except on a circle for a different size brake drurn lughole circle.

A pin assembly 150 is received in each recess 144 and 146 for engaging alug hole in the brake drum. The pin assembly 150 includes a support pin151 which is slidably received in recess 144 or 146. The exposed portionof each pin 151 is tapered at 152 and defines a central opening 154therethrough. An annular retaining flange 155 extends into the opening154 intermediate its ends which is engaged by the head 156 of anchormember 158 to retain pin 151 in recess 144 or 146. The anchor member 158is held in recess 144 or 146 by screw 159 in the plate 141. A spring 160received around anchor member 158 between flange 155 and the closed endof recess 144 or 146 constantly urges the pin 151 from the recessagainst head 156.

Clamping members as seen in FIG. 6 may be provided on base member 101spaced outwardly of the counterbore 104 to clamp the adapter 140 anddrum D in position for cutting the central opening 0. The members 170urge the drum D and pins 151 against springs 160 to firmly seat the drumD against that working face of the adapter 140 being used.

From the foregoing, it will be seen that the adapter 140 is placed incounterbore 104 so that the pins 151 arranged along a circlecorresponding to the lug hole circle of the drum D to be turned areextending upwardly. The drum D is then placed on the adapter 140 so thatthe lug holes H are positioned on the upturned pins 151. This aligns thedrum D so that its efiective rotational axis lies along the centerlineCL of the counterbore 104 and the cutting tool 122. The operator thengrasps handle 134 alter starting motor 129 and lowers tool 122 intocontact with the drum D around opening to redefine the opening 0 so thatit is concentric about the effective rotational axis of the drum. Afterthis operation is completed, the drum D can be mounted on a brake drumlathe and re-turned in conventional manner to properly define thebraking surface BS concentric with the efiective rotational axis of thedrum.

By using difierent adapters 140, it will be seen that that differentsize brake drums may be adjusted for re-turning the braking surface.Further, the adapter 140 provides for the proper support of the brakedrum D for two different sizes simply by turning the adapter over.

The tools 42 and 122 shown are reamers, however, it is to be understoodthat different types of cutting and grinding tools may be substitutedtherefor.

While specific embodiments of the invention have been described herein,it is to be understood that full use may be made of modifications,substitutions, and equivalents without departing from the scope of theinventive concept.

We claim:

1. Apparatus for redefining the central opening through a brake drum toestablish concentricity between the central opening and the circle alongwhich the lug holes through which the brake drum is supported on thevehicle lie, said ap paratus including:

support means for engaging the brake drum through its lug holes andsupporting the brake drum;

a tool for selected engagement with the brake drum about the centralopening therethrough; and,

positioning means for positioning said tool along the effectiverotational axis of the brake drum while carried by said support meansfor selected engagement of said tool about the central opening in thedrum to redefine the central opening concentrically with respect to theeffective rotational axis of the drum and the circle along which the lugholes lie.

2. The apparatus of claim 1 wherein said support means includes aplurality of support pins arranged in a configuration corresponding tothe arrangement of the lug holes in the brake drum and each having asize to be received in the lug holes and support the brake drum; and,wherein said positioning means locates said tool concentrically withinsaid pin arrangement.

3. The apparatus of claim 2 wherein said positioning means includes aspring for constantly urging said tool away from engagement with thebrake drum around the central opening.

4. The apparatus of claim 3 wherein said support means includes a secondplurality of support pins arranged in a configuration corresponding toanother arrangement of the lug holes in a brake drum and wherein saidfirst plurality of support pins and said second plurality of supportpins are arranged to alternately support a brake drum under said tool.

5. The apparatus of claim 4 further including drive means forselectively rotating said tool while it is in engagement with said brakedrum.

6. A device for redefining the central opening through a brake drum sothat the opening is concentric with respect to the lug hole arrangementin the brake drum, said device ineluding:

a housing defining a central bore therethrough, a counterbore recess atone end of said bore, and a plurality of pin receiving passagescircumferentially spaced about a circle concentric about the commoncenterline of said bore and counterbore; said pin receiving passagescorresponding in arrangement with the lug hole arrangement in the brakedrum;

a pin assembly mounted in each pin receiving passage in said housing andincluding a tapered portion extending from said housing on the same sidethereof as said counterbore, said tapered portion receivable in a lughole of the brake drum; and,

a cutter assembly mounted in said bore in said housing, said cutterassembly including a spindle rotatably joumaled in said bore forrotational and axial movement therein, a cutting tool attached to theend of said spindle extending into said counterbore, a spring connectedto said spindle for constantly urging said cutting tool toward saidcounterbore, and a handle connected to the opposite end of said spindlefor forcing said cutting tool from said counterbore and into engagementwith the brake drum about its central opening and for rotating saidcutting tool to redefine the central opening concentric with theefiective rotational axis of the brake drum.

7. A device for redefining the central opening through a brake drum sothat the central opening is concentric with respect to the lug holearrangement. in the brake drum, said device including:

a base member defining a counterbore therein;

an upright standard carried by said base member, oriented parallel tothe centerline of said counterbore, and laterally spaced from saidcounterbore;

a positioning arm slidably mounted on said standard for movement alongsaid standard, said arm including locking means for selectively fixingsaid arm with respect to said standard;

a tool assembly carried by the extending end of said arm, said toolassembly including a spindle rotatably and slidably joumaled in theextending end of said arm above said counterbore and lying along thecenterline of said counterbore, a tool adapted to engage the brake drumabout its central opening to redefine same mounted on the lower end ofsaid spindle and rotatable therewith, a spring connected to said spindleand said arm for constantly urging said spindle and said tool away fromsaid base member, and drive means for selectively rotating said spindleand said tool; and,

an adapter selectively positionable in said counterbore in said basemember to carry the brake drum thereon, said adapter including anannular support plate having a diameter just sufficient to be receivedin said counterbore and a first plurality of support pins correspondingin size and arrangement to the lug hole arrangement in the brake drum,said arrangement of support pins being concentrically located about thecenterline of said counterbore when said support plate is carriedtherein so that the centerline of said counterbore lies along theeffective rotational axis of the brake drum carried by said support pinsfor said tool to be lowered into contact with the drum about the centralopening to redefine the opening concentric about the effectiverotational axis of the drum and with the lug hole arrangement.

8. A device as set forth in claim 7 wherein said adapter includes asecond plurality of support pins on the opposite side of said supportplate from said first plurality of support pins, said second pluralityof support pins corresponding in size and arrangement to a different lughole arrangement in a brake drum and located concentrically about thecenterline of said counterbore when said support plate is carried bysaid counterbore so that, by turning said support plate over, adifferent size brake drum can be trued and wherein each pin is springurged from said support plate; and further including clamping means forclamping the brake drum onto said adapter.

9. A method for relocating the central opening in a brake drum supportedon a vehicle through its lug holes including the steps of:

a. supporting the brake drum to have its central opening relocated;

b. positioning a tool concentrically within the circle defined by thelug holes; and, i

c. engaging the brake drum with the tool while maintaining the toolconcentrically within the lug hole circle so that the central opening isredefined to conform to the cutting tool.

10. A method as set forth in claim 9 wherein the step of sup- 75 portingthe brake drum includes positioning the brake drum so that its lug holesare received over a plurality of support pins arranged concentricallyabout the centerline of the tool.

1. Apparatus for redefining the central opening through a brake drum toestablish concentricity between the central opening and the circle alongwhich the lug holes through which the brake drum is supported on thevehicle lie, said apparatus including: support means for engaging thebrake drum through its lug holes and supporting the brake drum; a toolfor selected engagement with the brake drum about the central openingtherethrough; and, positioning means for positioning said tool along theeffective rotational axis of the brake drum while carried by saidsupport means for selected engagement of said tool about the centralopening in the drum to redefine the central opening concentrically withrespect to the effective rotational axis of the drum and the circlealong which the lug holes lie.
 2. The apparatus of claim 1 wherein saidsupport means includes a plurality of support pins arranged in aconfiguration corresponding to the arrangement of the lug holes in thebrake drum and each having a size to be received in the lug holes andsupport the brake drum; and, wherein said positioning means locates saidtool concentrically within said pin arrangement.
 3. The apparatus ofclaim 2 wherein said positioning means includes a spring for constantlyurging said tool away from engagement with the brake drum around thecentral opening.
 4. The apparatus of claim 3 wherein said support meansincludes a second plurality of support pins arranged in a configurationcorresponding to another arrangement of the lug holes in a brake drumand wherein said first plurality of support pins and said secondplurality of support pins are arranged to alternately support a brakedrum under said tool.
 5. The apparatus of claim 4 further includingdrive means for selectively rotating said tool while it is in engagementwith said brake drum.
 6. A device for redefining the central openingthrough a brake drum so that the opening is concentric with respect tothe lug hole arrangement in the brake drum, said device including: ahousing defining a central bore therethrough, a counterbore recess atone end of said bore, and a plurality of pin receiving passagescircumferentially spaced about a circle concentric about the commoncenterline of said bore and counterbore; said pin receiving passagescorresponding in arrangement with the lug hole arrangement in the brakedrum; a pin assembly mounted in each pin receiving passage in saidhousing and including a tapered portion extending from said housing onthe same side thereof as said counterbore, said tapered portionreceivable in a lug hole of the brake drum; and, a cutter assemblymounted in said bore in said housing, said cutter assembly including aspindle rotatably journaled in said bore for rotational and axialmovement therein, a cutting tool attached to the end of said spindleextending into said counterbore, a spring connected to said spindle forconstantly urging said cutting tool toward said counterbore, and ahandle connected to the opposite end of said spindle for forcing saidcutting tool from said counterbore and into engagement with the brakedrum about its central opening and for rotating said cutting tool toredefine the central opening concentric with the effective rotationalaxis of the brake drum.
 7. A device for redefining the central openingthrough a brake drum so that the central opening is concentric withrespect to the lug hole arrangement in the brake drum, said deviceincluding: a base member defining a counterbore therein; an uprightstandard carried by said base member, oriented parallel to thecenterline of said counterbore, and laterally spaced from saidcounterbore; a positioning arm slidably mounted on said standard formovement along said standard, said arm including locking means forselectively fixing said arm with respect to said standard; a toolassembly carried by the extending end of said arm, said tool assemblyincluding a spindle rotatably and slidably journaled in the extendingend of said arm above said counterbore and lying along the centerline ofsaid counterbore, a tool adapted to engage the brake drum about itscentral opening to redefine same mounted on the lower end of saidspindle and rotatable therewith, a spring connected to said spindle andsaid arm for constantly urging said spindle and said tool away from saidbase member, and drive means for selectively rotating said spindle andsaid tool; and, an adapter selectively positionable in said counterborein said base member to carry the brake drum thereon, said adapterincluding an annular support plate having a diameter just sufficieNt tobe received in said counterbore and a first plurality of support pinscorresponding in size and arrangement to the lug hole arrangement in thebrake drum, said arrangement of support pins being concentricallylocated about the centerline of said counterbore when said support plateis carried therein so that the centerline of said counterbore lies alongthe effective rotational axis of the brake drum carried by said supportpins for said tool to be lowered into contact with the drum about thecentral opening to redefine the opening concentric about the effectiverotational axis of the drum and with the lug hole arrangement.
 8. Adevice as set forth in claim 7 wherein said adapter includes a secondplurality of support pins on the opposite side of said support platefrom said first plurality of support pins, said second plurality ofsupport pins corresponding in size and arrangement to a different lughole arrangement in a brake drum and located concentrically about thecenterline of said counterbore when said support plate is carried bysaid counterbore so that, by turning said support plate over, adifferent size brake drum can be trued and wherein each pin is springurged from said support plate; and further including clamping means forclamping the brake drum onto said adapter.
 9. A method for relocatingthe central opening in a brake drum supported on a vehicle through itslug holes including the steps of: a. supporting the brake drum to haveits central opening relocated; b. positioning a tool concentricallywithin the circle defined by the lug holes; and, c. engaging the brakedrum with the tool while maintaining the tool concentrically within thelug hole circle so that the central opening is redefined to conform tothe cutting tool.
 10. A method as set forth in claim 9 wherein the stepof supporting the brake drum includes positioning the brake drum so thatits lug holes are received over a plurality of support pins arrangedconcentrically about the centerline of the tool.